California’s Kindergarten Readiness Act of 2010 established transitional kindergarten (TK), the first year of a two-year kindergarten program for students affected by the change in the birthdate cutoff for entry into kindergarten from December 2 to September 1. This final report from the program’s evaluation focuses on results from a five-year study. The study used a rigorous regression discontinuity design to examine whether TK, as a new approach to prekindergarten education for age-eligible students, leads to positive outcomes, for which students, and under what conditions.

Transitional kindergarten—the first year of a two-year kindergarten program for California children born between September 2 and December 2—is intended to better prepare young five-year-olds for kindergarten and ensure a strong start to their educational career. AIR researchers examined the success of the program by determining the impact of transitional kindergarten on students’ readiness for kindergarten in language, literacy, mathematics, executive functioning, and social-emotional skills.